1. Field of the Invention
The present invention relates to an image forming apparatus for charging transfer residual toner on an intermediate transfer member and transferring the charged transfer residual toner onto an image bearing member, thereby removing the toner from the intermediate transfer member.
2. Description of the Related Art
Hitherto, an image forming apparatus of an intermediate transfer system using an intermediate transfer member has been known as an image forming apparatus of an electrophotographic system such as a copying apparatus, laser beam printer, or the like. The image forming apparatus of the intermediate transfer system forms a color image (multicolor image) or the like onto a recording material by a primary transfer process and a secondary transfer process.
That is, first, as a primary transfer process, a toner image as a transferable image formed on the surface of an electrophotographic photosensitive member (hereinbelow, simply referred to as a “photosensitive member”) serving as an image bearing member is transferred (primary transfer) onto the intermediate transfer member also serving as an image bearing member.
By overlappingly executing the primary transfer process with respect to toner images of a plurality of colors, a multiple toner image constructed by the toner images of the plurality of colors is formed on the surface of the intermediate transfer member. Subsequently, as a secondary transfer process, the toner image on which the toner materials of the plurality of colors have been overlaid and which has been formed on the surface of the intermediate transfer member is transferred (secondary transfer) in a lump onto the surface of a recording material such as paper or the like.
In the image forming apparatus of the intermediate transfer system, after the secondary transfer of the toner image from the intermediate transfer member onto the recording material was executed, the toner remains as secondary transfer remaining toner (transfer remaining toner, residual toner) on the surface of the intermediate transfer member. Therefore, in order to remove the transfer remaining toner which remains on the surface of the intermediate transfer member, the following image forming apparatus has been proposed as disclosed in Japanese Patent Application Laid-Open No. 9-50167. The image forming apparatus disclosed in Japanese Patent Application Laid-Open No. 9-50167 has a charging unit arranged on a downstream side of a secondary transfer position in a moving direction of a surface of an intermediate transfer member and a charging unit arranged on an upstream side of a primary transfer nip. The charging units charge secondary transfer remaining toner to a polarity opposite to that of a surface electric potential of a first image bearing member. That is, the secondary transfer remaining toner is charged to the polarity opposite to a normal charge polarity of the toner. The secondary transfer remaining toner of the opposite polarity on the intermediate transfer member is transferred and returned to the surface of a photosensitive member through the primary transfer nip simultaneously with the primary transfer (system in which the toner is collected simultaneously with the transfer). The transfer remaining toner returned to the photosensitive member is collected by a cleaning member which faces the photosensitive member.
In Japanese Patent Application Laid-Open No. 2004-21134, an image forming apparatus of a tandem system having a charger (contact type charge member) for charging secondary transfer remaining toner to a polarity opposite to a normal charge polarity has been proposed. The image forming apparatus of the tandem system has a plurality of image forming units (hereinbelow, referred to as “a station” or “stations”) each of which has an image bearing member and a waste toner container for enclosing toner removed from the surface on the image bearing member and forms an image by different kind (color) of toner. According to the image forming apparatus of the tandem system, a large quantity of secondary transfer remaining toner is enclosed into the specific waste toner container and an exchange frequency of only its cartridge increases, so that it is uneconomical. Therefore, in the image forming apparatus disclosed in Japanese Patent Application Laid-Open No. 2004-21134, by increasing a capacity of the waste toner container of only the cartridge in which a large quantity of secondary transfer remaining toner is enclosed, the exchange frequency of the cartridge in which the large quantity of secondary transfer remaining toner is enclosed is decreased. However, there is such an inconvenience that the cartridge enlarges by increasing the capacity of the waste toner container. In addition, if the waste toner is repetitively collected into the cartridge which is not used for image forming, the waste toner container having the large capacity will be filled with the waste toner soon.
As another related art, in U.S. Pat. No. 6,473,574, in an image forming apparatus of a tandem system, a method whereby one of a toner caused at a time of a test image forming or a jam occurrence and a toner remaining as fogging toner on a moving member is distributed to different stations and collected has been proposed. However, according to the invention disclosed in U.S. Pat. No. 6,473,574, timing for a primary transfer and timing for cleaning transfer remaining toner on an intermediate transfer member differ and it takes time for the cleaning.